The present invention relates to a system for delivering cooling air to a seal arrangement in a turbine stage of a gas turbine engine.
Many gas turbine engines have a second stage turbine stator vane assembly disposed between rotors. The stator vane assembly includes a plurality of stator vane segments collectively forming an annular structure. A seal ring, located radially inside of the inner platforms of the stator vane segments, is used to maintain a pressure difference between a first annular region adjacent the first stage rotor and a second annular region adjacent the second stage rotor. The seal ring includes an outer flange and an inner flange. The outer flange includes splines to prevent rotation and an abradable bearing pad. A honeycomb pad is attached to the inner flange for use with knife edge seals. The splines disposed in the outer flange are slidably received, in an axial direction, within inner mounting flanges extending below the inner platforms. Hooks, extending out from the outer flange, limit the axial travel of the seal ring relative to the inner mounting flanges. The pressure difference between the first annular region adjacent the first rotor stage and the second annular region adjacent the second stage rotor forces the abradable bearing pad of the seal ring into contact with the aft arm of the inner mounting flanges. Such a seal arrangement is shown in U.S. Pat. No. 5,785,492 to Belsom et al., which is hereby incorporated by reference herein.
In certain turbines, the rotor seals have a life shortfall. This is because a vane is used to supply cooling air to the cavity adjacent the high pressure turbine gaspath, where cooling flow rate and temperature drive the seal life. The cooling air travels through the vane before reaching the seal rim cavity. Gaspath air heats the vane and the cooling air passing through the vane. If the cooling air temperature is too high, the seal assembly does not meet design life intent.
Thus, there is a need for a more efficient approach for delivering cooling air to the seal rim cavity.